Insidious Reef is a wicked wall dive located on a small crest just south of the more common fringe reef.

Most of the dives from Roatan are made along the fringing reef, which parallels the shoreline, but Insidious Reef is located on a crest half a mile south of the reef. Its sheer plunging wall is exquisite and pristine. The top of the reef is in deep water, starting at 16 – 18 m. From the top of the crest the wall literally drops into the abyss of the Bartlett Trench to more than 1500m. At the reef crest, ridge after ridge is punctuated with huge forests of staghorn and pillar corals. On the fore reef, enormous boulder corals form shingled overhangs and ledges. Black coral and azure vase sponges grow in profusion. There is nothing like gliding by a black coral forest to stimulate excitement. Deepwater lace adds character and beauty to an already fabulous cliff structure.

The marine life here is that usually associated with deeper offshore waters. Sea turtles grace the scenery. Black crinoids sit atop large barrel sponges. Queen and ocean triggerfish, scrawled filefish, and schools of jacks, tobacco fish, hogfish, blackcap basslets, and black durgeons are abundant. Occasional sharks may be seen passing by.